A novel problem formulation for directional overcurrent relay coordination

In general, directional overcurrent relays allow for continuous time dial settings but discrete pickup current settings. All previous work formulates the coordination problem either as a linear programming problem or as a nonlinear programming problem. In this paper, the protective relay coordination problem is reformulated to take into account the discrete pickup current values. The coordination problem is formulated as a mixed integer nonlinear programming (IMINLP) problem and is solved using general algebraic modeling system (GAMS) software.